1. Field of Invention
This invention relates to a sports device in which the rider glides over a fluid; specifically, this invention relates to a surfboard type device for riding on water, propelled by the force of a boat wake or a wave generated by a wave generating device.
2. Background of the Invention
Specially configured boards for gliding along a fluid are known, such as snowboards, snow skis, snow skates, snow sleds, water skis, wake boards, surfboards, skim boards, body boards, air boards, river boards, and the like. For purposes of this patent, “gliding board” will refer generally to any of the foregoing boards as well as to other board-type devices which allow a rider to traverse a fluid. For ease of understanding, and without limiting the scope of the invention, the inventive shape for the lower surface of a gliding board to which this patent is addressed is disclosed below, particularly in connection with a surfboard, designed to ride in the wake produced by a boat.
People have ridden surfboards on the ocean and behind boats for decades. The sport of wake surfing, riding a surfboard on the wake of a boat, has recently received new popularity. There are numerous reasons for this increase in popularity including:                a) the availability of sport boats that produce large wakes; and        b) the injury rate of wake boarding, waterskiing and other higher speed water sports, and the desire of people to enjoy water sports with a lower injury rate; and,        c) the development of smaller surfboards applicable to surf behind the boat.        
There are several reasons why a smaller surfboard is beneficial in this context:                a) the person rides so close to the back of the boat that a longer surfboard strikes the boat, impeding the ride; and        b) longer surfboards are less maneuverable; and        c) longer surfboards are difficult to stow on the boat.        
Traditional surfboards are generally made with a foam or balsa wood core covered with fiberglass and resin. This construction technique typically results in a surfboard that is:                a) fragile; and        b) expensive to make; and        c) too thick to fit in a standard wake board rack on the boat.        
Many of the current wake surfboard designs have a tendency to unexpectedly nose dive into the water, thus upsetting the rider. Also, most traditional surfboards are unstable with side-to-side movements, and particularly for beginners, are like trying to stand on a log that wants to roll under you.
Flat skim boards with fins attached have also been utilized for wake surfing. A flat skim board does not provide the same control to the rider as does the current invention.
Water skis have been made with a longitudinal tunnel for decades. There has also been a recent patent for a snowboard that is tunnel shaped along the longitudinal axis. This prior art differs from the current invention in that the tunnel shape has occurred along a flat longitudinal axis with an upturned end or pair of ends, as opposed to possessing a saddle shape, or anticlastic shape, as does the current invention.
In an article in Wake Boarding (magazine), February 2003, p. 61, in the section sub-titled “Bottom Design”, there is a reference to concaves on the bottom of wake boards. These concaves do not run the length of the board and would better be described as tunnels or channels, as the remainder of the bottom surface of the boards are flat along the transverse axis.